Sash Window Repair

'Still in the Frame'

Jeanette
Bowden and Abigail Cragg

Sash windows can be centuries old but with modern repair and upgrading
techniques these classics can continue to perform perfectly well.

A
Queen Anne building, left, with exposed box-frames around
the windows, and a Georgian house, centre, showing the impact
of moving the frames back behind the brickwork on the character
of buildings. By the time this Victorian terraced house (right)
was built it had become possible to use much larger panes,
and again the character of the architecture changed dramatically
as a result.

The classic
box sash window has been a feature of Britain's architecture for
over three centuries. Thought to be of French origin, this
timeless style was adopted in Britain as early as the 17th century,
and is truly part of our heritage. Countless properties, diverse
in style and stature, share this common trait. From traditional
towns and cities, to rural villages and conservation areas, the
sash window can be found practically everywhere: in stately homes,
Georgian period properties, Victorian and Edwardian terraces,
charming cottages and listed buildings of all types.

The development
in style of the sash tracks historical events, architectural evolution,
even quirkiness. While the majority of sash windows consist of
box frames, where the weights are hung vertically to counterbalance
the sashes, local variants of sideways sliding sashes (or
'Yorkshire' sashes) are present in many English counties.

A significant
style change was invoked as a result of the Great Fire of London
and the building acts which followed in 1709 and 1774. The first
stipulated that frames in the capital should be set back a minimum
of four inches from the facade so that fire could not travel so
easily from one window to the next. The second required that the
boxes be set back behind the masonry. The result was that the
sash boxes on either side of the sashes disappeared from exterior
elevations, and the window openings became narrower and more elegant.

An additional
influence during this period was the introduction of a window
tax, which meant that certain non-essential windows were bricked
up to avoid tax liability. At this time, an arrangement of six
panes in each sash was fairly common, because glass was expensive
to manufacture and only available in small sizes. Glazing bars,
which had been thick and heavy in the late 17th century, were
now thinner and more refined and by the late 18th century larger
panes were being manufactured from cylinder glass, enabling much
larger panes than the old crown glass method of production. By
the mid 19th century many older multi-paned windows were substituted
with four-paned windows and, by the turn of the 20th century,
houses were being built with large sash windows, with each sash
consisting of one large pane.

Described
by one expert as 'the eyes of the facade' to highlight their importance
to its character, original windows have obvious aesthetic attributes.
Handcrafted in original timber, they are stylistically in keeping
within the context of a traditional property. Coupled with their
architectural significance, not to mention natural longevity,
it could be argued that they have earned their enduring status.
However, the threat to the sash window is ever-present. Flaking
paint and decay can appear unattractive relative to pristine PVCu,
or modern timber counterparts.

Most who have
had first hand experience of the sash, even ostensibly in relatively
good working order, will be familiar with their common deficiencies.
Draughts and rattles, not to mention noise penetration and sticking
problems, are regular afflictions. At the other end of the scale,
rotting frames and meeting rails, damaged glazing bars, faulty
weights, or broken glass are all too common. These factors, taken
individually, not to mention collectively, can suggest that replacement
is the obvious and, some would contest, only logical solution.
To frustrated homeowners and inhabitants of commercial properties
- particularly those used as a working environment - there often
appears little choice but to resort to 'plastic surgery' for original
windows and doors, or their replacement with modern imitations
in either plastic or timber. Perceptions persist that the 'PVCu
pretender' can provide longer life and have lower maintenance
requirements.

Before deciding
to replace original windows, however, it is worthwhile remembering
a few salient factors. Taking aside sentimentality, the traditional
sash has several practical advantages. Firstly, original sash
windows have been made by a skilled craftsman, individually, using
the highest standard of timber and materials. A testimony to the
longevity of the design is that it has already withstood centuries
of wear. In contrast, many modern materials used in windows have
begun to yellow and crack after 10 to 15 years of usage. Even
new timber windows, made to original concepts, do not necessarily
have the endurance of their older counterparts. This is because
in the Georgian and Victorian periods the softwood timber in general
supply was second to none. It came from the Baltic where it had
grown slowly in the cold environment, producing a very dense,
tight-grained wood. Timber of such quality is difficult to find
today.

Despite perceptions
to the contrary, a window produced in the 18th or 19th century
can often be salvaged virtually intact and renovated to provide
excellent standards of performance. Experience of dealing with
sash window renovation over many years indicates that as much
as 95 per cent of the timber in an original window can be retained.
Rotten timber can be routed and repairs made using a synthetic
wood repair system. This means that even windows considered beyond
repair may have only superficial deterioration and, once overhauled,
can continue to provide, quite literally, centuries of further
loyal service.

Whilst the
individual condition of windows can vary dramatically, even within
the same property, an expert survey will itemise the scope and
extent of renovation required on a bespoke basis. Window renovation
and overhaul should not be considered to be a cheap 'quick-fix'
solution; it is a craftsman-driven method of restoring an original
window to good working order for many years to come.

Despite
its appearance, the wood in this window is generally sound,
and it can easily be repaired to provide many decades of further
service.

A comprehensive
window overhaul will commence with bonded repairs of rotten wood
using a two-part epoxy resin, or, in the case of extreme decay,
replacement of complete sections of the frame. Delicate glazing
bars can be replicated to match the originals. Similarly, while
modern production techniques have ensured that glass is now flawless,
it is possible to source glass with manufactured imperfections
to emulate the original glazing where panes have cracked or broken.
Original crown, muff, or cylinder glass has tints and bubbles
which would cause natural refractions of the light, and is often
considered to add charm and character.

Sash weights,
housed within the frame and used to counterbalance the sashes,
can often be misaligned, imbalanced, or completely missing, causing
the sashes to stick when opening and closing. As part of a comprehensive
window renovation, these should be rebalanced. Sash cords are
also subject to decay, but these, together with pulleys, can be
replaced to ensure that they slide smoothly.

In addition
to standard repair and refurbishment, it is possible to upgrade
a sash window to levels of performance comparable with modern
replacements.

A little-recognised
benefit of an original sash window is that it remains one of the
most efficient designs for controlling ventilation. A well-maintained
and designed sash window usually has a 3mm gap around its moving
faces to allow the window to be opened and closed easily. However,
over the years, routine wear and tear, combined with painting
and decoration will result in the operational tolerances changing
substantially - hence the draughts and rattles. The significance
of poor sealing around a frame can create an equivalent draught
effect to that of having a 125mm hole in the centre of a window.

Conversely,
improvements in comfort levels and energy savings usually associated
with double-glazed replacement windows are largely attributable
to the weatherseals, with very little comfort and energy savings
being linked to the 'u - value' (or energy saving effect) of the
glazing itself. However, windows do not have to be replaced to
gain these energy saving benefits, since existing windows and
doors can be upgraded without any significant loss of character
or material.

Introducing
an appropriate, well designed sealing system offers a number of
other important benefits:

air changes per hour are reduced to a building's natural
rate, giving greatly improved comfort levels and a considerable
potential to reduce energy consumption

draughts and rattles can be virtually eliminated

sashes are easy to slide open and closed

by reducing the air gaps surrounding the sashes, dramatic
improvements in noise attenuation can be achieved, with the
potential to reduce the effects of external noise by up to
10dB.

Left:
Re-cording a sash window using the traditional figure of eight
cording method (Photo: Mark Davey, Ventrolla). Middle and
right: Most of the heat loss from an original sash window
is due to the gaps, not the glass, and the windows rattle
in the wind. Draught stripping resolves the problem without
losing the original glass or the frame.

A further
perceived drawback of the original sash system is the perennial
problem of cleaning and decoration. Being at best cumbersome to
manoeuvre, and at worst jammed solid, sash windows can quickly
lose appeal. This problem can be overcome on a lasting basis through
the introduction of a system of fittings which enables both sashes
to be easily removed internally. This will allow cleaning and
maintenance to be carried out from within a building and in the
case of larger properties, without the need for scaffolding.

With homeowners
increasingly seeking to preserve the traditional appearance of
their properties, it is to be hoped that knowledge of alternative
solutions to window related problems will continue to grow. Conservation
officers, specialist architects and surveyors and other conservation
professionals are playing a vital role in providing guidance and
advice to the owners of listed buildings on the options available
to them, but still far too many fine and historic windows are
being replaced unnecessarily.

Before making
a decision to discard sash windows, even if they appear beyond
redemption, it is always worthwhile consulting experts. They can
help to determine the extent of deterioration and guide the process
of renovation or, where really necessary, replacement.

This
article is reproduced fromThe
Building Conservation Directory, 2006

Author

This
article was prepared by JEANETTE BOWDEN and ABIGAIL CRAGG of Ventrolla Limited.